Centrifugal compressor



Jun 16, 1942. I M, WATSON 2,286,522

CENTRIFUGAL COMPRESSOR Filed April l3, 1940 v Sheets-Sheet 1 Ralph M.-Walson m N R ATTORNEY June '16; 1942.

R. M. WATSON GENTRIFUGAL COMPRESSOR Filed April 15, 1940 I 7Sheets-Sheet 2 Ralph INVE ATTORN EY June16, 1942. R. M. WATSON 2,21%,522

GENTRIFUGAL COMPRESSOR Filed April 13, 1940 7 Sheets-Sheet 3 Ralph M.Watson IN ENTOR ATTORNEY June16,1942- R. M. WATSON 2,286,522

CENTRIFUGAL COMPRESSOR Filed April 13, 1940 I '7 Sheets-Sheet 4 Ra/pl? MWatson IN R ATTORNEY June 16, 1942. R. M. wA'rsoN CENTRIFUGAL COMPRESSORFiled April 13, 1940 7 Sheets-Sheet 5 v I I June 16, 1942. R. M. WATSON2,286,522

CENTRIFUGAL COMfRESSOR Filed April 15, 1940 7 Sheets-Sheet 6 Fig 6 I G au Z' F157 9 2 j 2 v 65 Ralph M. Watson 2| 6.) IN R ATTORNEY CENTRIFUGALCOMPRESSOR Filed April 13, 1940 7 Sheets-Sheet '7 I Ralph M. WatsonINVENTOR ATTORNEY Patented June 16, 1942 CENTRI'FUGAL COMPRESSOR RalphM. Watson, Bloomfield, N. J., assignor to Worthington Pump and MachineryCorporation, Harrison, N. J., a corporation of Delaware ApplicationApril 13, 1940, Serial No. 329,498

9 Claims.

commonly in use, complicated and expensive mechanisms or structures arenecessary due to the design of the compressors employed, for balancingthe end thrust in the compressor and sealing the openings in the casingthrough which the driving shaft extends against the compressor pressuresto prevent leakage of the refrigerant vapors to the atmosphere andleakage of air into the compressor.

An object of the present invention is to provide a centrifugalcompressor in which volutes are employed, in connection with impellers,arranged in a novel manner to provide a highly efficient, compactcompressor in which any end thrust is substantially eliminated bybalancing of the impellers in such manner that certain of them provide acounter-balancing end-:wise thrust against the end-wise thrust of theother impellers, thereby eliminating expensive and complicated thrustbalancing means.

Another object of the invention is to provide a. centrifugal compressorin which the impellers are arranged whereby the seals or packing at theopenings in the casing through which the shaft pressor of the preferredform embodying the invention, and the features forming the inventionwill be specifically pointed out in the claims.

In the drawings: Figpre 1 is a side elevation of the improvedcentrifugal compressor. I

Figure 2 is'a top plan view of the compressor. Figure 3 is an end viewof the compressor looking toward the suction or inlet end.

Figure 4 is a longitudinal section through the compressor taken on theline 44 of Figure 2. Figure 5 is a cross-section of the compressor takenon line 55 of .Figure 4.

Figure 6 a vertical cross-section through the'suction inlet of thecompressor taken approximately on the line 6-6 of Figure 4.

Figure 7 is a' horizontal longitudinal section through the compressorcasing alone, showing the volutes and passages, taken on the line ofFigure '3.

Figure 8 is a vertical cross-section through the final discharge voluteof the compressor taken approximately on the line 88 of Figure 4.

Figure 9 is an enlarged view, in section, of

a portion of the compressorshowing the casing bushing. I

discharge volute in lieu of the general practice of employing diffusionvanes in the discharge passage of the compressor with the result thatextends are subjected to pressures below the disleakage of vapor orgas'through the shaft bearings and to provide a lubricating systemembodying a plurality of chambers under various degrees of pressure inthe return line of the lubricant from the bearings to the circulatingoil pump so as to separate the entrained refrigerant from the oil.

With these and other objects in view, as may appear from theaccompanying specification, the v invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing a centrifugalcomthe efliciency of the compressor is materially.

increased and frictional losses diminished. The compressor comprises ahorizontally split casing l0, through the axis of which extends thedriving shaft H. The driving end of the shaft H may be connected by anyapproved type of coupling l2 with any approved type of prime mover. Theshaft ll carries the various impellers of the centrifugal compressor,thenumber of which and consequently the number of stages of the compressordepends entirely upon the conditions of the installation in which thecompressor is to be incorporated and the work to be performed by thecompressor.

In the presentapplication a three stage compressor isillu'strated, butit is to be understood that the principles of the invention as set outin the claims are equally applicable to centrifugal compressors,regardless of the number of passage l4 has a butterfly valve or damperI5 therein, by. means of which the active, vapor passing cross-sectionalarea of the passage l4 may be regulated. This butterfly valve l5 may beoperated by any suitable mechanism. A hand wheel operated gear andpinion structure is shown in Figures 1 and 3 of the drawings, in whichthe gear I5 is rotated by the pinion IS. The pinion I6 is in turnrotated by a hand wheel H. The gear I5 is mounted upon or suitablyconnected to the carrying shaft l8 of the valve l5. The inlet passage l4curves upwardly and laterally into the suction or inlet eye 20 of thefirst or suction stage impeller 2|.

The inlet passage H is partially bifurcated by means of dividingvapor-directing ribs 22 and 23, the latter of which is substantially aninwardly extending projection of the uppermost portion of the side wallof the inlet passage where the two side sections or portions meet, asclearly shown in Figure 6 of the drawings. This particular constructionof the suction inlet passage facilitates the distribution of therefrigerant vapors in the suction or inlet eye of the first stageimpeller 2| and suppresses the creation of eddies and vacuous pockets inthe inlet passage. By particular reference to Figures 4 and 6 of thedrawings it will be noted that the inlet passage l4 curves in a smoothcurvature in all directions towards the inlet eye 2l|.

The first stage impeller 2| of the compressor discharges into a doubleor twin volute 30 formed of the two volute passages 3| and 32, clearlyshown in Figures 4 and 5 of the drawings. The defining walls 33 of thedouble volute passages curve circumferentially and laterally into thesuction passage 34, which opens into the inlet or suction eye 35 of thesecond stage impeller 35.

The provision of the double or twin volute 30 decreases the machinedimensipns and balances any radial thrust which would-arise in the firststage of the compressor due to operation at conditions other than thosefor which the specific compressor was designed. This provision of thetwin or double volute, together with the staggered arrangement of thevolutes of the remaining stages of the compressor, will approximatelytake care of or balance any radial thrust which may occur in the entirecompressor during off standard operating conditions.

The second stage impeller 36 discharges into a single volute 31, whichis connected by a suitable passage to the suction eye 38 of the thirdstage impeller 39. The passage which connects the discharge volute 31 ofthe second stage impeller 36 to the third stage impeller 39 is shown inthe drawings as comprising the nozzles 40 and ll, which are formed onthe casing of the compressor and are connected by a U-coupling 42. TheU-coupling 42 has a connection formed thereon which opens into thepassage 44, which establishes communication between the second and thirdstage impellers so as to permit the introduction of vapors into anintermediate stage of the compressor. While the coupling 43 is shownarranged to permit the introduction of vapor into the third stage of thecompressor, it is to be understood that such a connection may beconnected. at any suitable point to the casing of the compressor topermit the introduction of vapor into any one of the stages of thecompressor following the first stage. The third stage impeller 39, whichin the construction shown in the By utilizing volutes at the dischargeof the various stages in lieu of difluser vane structures, and by thevarious construction of cross-over connecting passages between thestages, a compact, relatively inexpensive centrifugal compressor may beprovided in which the various 1mpeller stages may be arranged to effectan approximate balance in the compressor, thereby eliminating the needof employing expensive and relatively complicated end thrust balancingmechanism.

In the drawings, wherein a three stage compressor is shown, it will benoted that the first two stages, that is the impellers-2| and 35, aredisposed in a parallel pair, with the back of the first stage impeller2i facing the suction of the second stage impeller 36. Thus the combinedend thrust of these two stages will be toward the right (Fig. 4), whilethe impeller 39 of the third stage of the compressor is disposed in adirection opposite to that of the impellers 2| and 36, with its backfacing the back of the second stage impeller 36. Consequently the endthrust of the third stage impeller 33 will be toward the left (Fig. 4)and in an opposite direction to the end thrust of the impellers 2| and36. Since impeller 39 is the highest pressure impeller and the endthrust produced by this impeller" will be substantially equal to the endthrust produced by impellers 2| and 36, counterbalancing end thrusts areset up in opposite directions in the compressor which will approximatelybalance each other and. permit the use of a-simple, inexpensive thrustbalancing bearing as shown at 51 in absolute discharge pressure of eachstage bearing a substantially constant ratio to its inlet pressure, andby reference to Figure 4 of the drawings it will be noted that thesuccessive stages of compression in the compressor decrease in volu-'metric capacity. That is, the secondstage impeller 35, whilebeing ofsubstantially the same,

diameter as the first stage impeller 2|, is narrower and consequently.has less volumetric capacity than the first stage impeller, while thethird stage impeller 39, which is also of substantially'rthe samediameter as the impeller 2| and 36; is narrower than the impeller 35 andconsequently has less volumetric capacity.

While the drawings show a three stage compressor with the impellersarranged as above specifically described, it is to be understood thatthe essence of this balancnig feature of the present invention comprisesthe arranging of the impellers in a multi-stage compressor in such amanner that the stages are divided, each set disposed in the oppositedirection to the other set, creating end thrust substantially equal tothe end thrust created by the impellers of the other set, for thepurpose of counterbalancing end thrust in the compressor.

Centrifugal compressors of the type above de-. scribed and illustratedin the drawings, when used or employed in refrigeration or airconditioning systems generally receive the vapor or refrigerant gasesinto the first stage suction at a pressure of approximately seven pounds(7 lbs.) below atmosphere. The third or final stage of the compressorreceives the vapor into its suction at a pressure slightly above orbelow atmosphere,

for instance atmosphere plus or minus three aagataa h,

pounds (3 lbs). Thus it will be seen that the opposite ends 01; theinterior of the casing it; will be subjected tosubatmospheric pressurejainitial inlet end of the casing and'to approxl mately atmosphericpressure at the other end of' the casing, that is, the end adjacenttothe dr ing end of the shaf-t'l I. It is desirable; er course,

to prevent leakage of air into the compressor easel ing, and also toprevent the leakage of 'val ablet refrigerant vapors from the compressorTherefore the present coninto atmosphere.

struction embodies means for efiectivel'ys'ealing l the openings in theends oithe which the shaft Ii extends.

In the present invention sealing of these casing through c ings iseffected during the operation'of the compressor through a combinationenclose-fitting bearings for the shaft and the lubricating 'sys:

tem for such bearings, while a special mechanism I is provided forsealing the casing when the-come pressor is idle.

Due to the arrangement of the" impellers in the compressor as abovespecifically described, not

only is end thrust in the compressor approxi mately counterbalanced, butthe'arrangemnt also provides that the shaft opening at the initialsuction end of the compressor is'subjecte'd to the pressure of the vaporat the initial inlet, while the shaft opening 5| at the oppositeend ofthe casing is subjected to the-suction'pres'si re of the vapor at thethird stage suction. There fore neither of these openings will besubjected to the highest'pressure developed ii the com pressor, whichfactmaterially' simplifies and'preduces the cost of themechanismforsealingisuch openings in that, for one-thing,[itreduc es thepressure of the lubricating oil.

An oil reservoir 52 is provided in which 'z'in oi l pump 53, of anyapproved construction; is

mounted. The oil pump- 53 is driven fro m shaft ll through a couplingstructure '54, shaft 55 and suitable transmission 56, which in thepresent instance is shown as beveled gears."

At the initial suction end of the compressor-a bearing structure 51 isprovided which is carried by the casing l0 and which hassuitableloil'ducts-" 58 extending radially t-herethrough. to -lubricatej;

the bearing. Oil is supplied to the ducts :58 from an oil inlet line 59which receivesttheuoiifrom the discharge end of an oil cooler 60,. Theoil is pumped by the pump 53 througha suitable piping system 6! into andthrough the --cooler. ,60. Pressure regulating valves 62 of anyapproved;

type or construction may be connectedinhthefl pipe line 6! for thepurpose of regulating the pressure of, the oil if it is desired. a The.oilpasses through the bearingil in both directionsand;

that which passes through thebearinginwardlys toward the compressorpasses intoachamber 63 I and returns through a drain opening eor drainopenings 64 through the bearing into the chamber 65. The oil whichpasses through-the bearing outwardly or away from the casing-Hipassesinto the chamber 65 and from this chamber "v drains into thereservoir 52. The chamber '65 is under a subatmospheric pressure.That-is, it; under the pressure of the vapor aswit enters the I initialinlet of the compressor. A stationary bushing 66 is mounted about theshaft Il,be

tween the bearing 51 and theim'peller 2|. Y This .pheric"pres'sure. *Oilis delivered to the-in .ter'n Bil-back to the reservoir 52."

formed therein with which a drainopening 69 communicates- The drain"opening leads bee]; 'to the chamber 63 'so 'that"z'ajn'y oil which wouldpass through 'the" bushing- 56 into: the chamber '68 wouldbe'draine'dback eventually intoth'e reser Kt theleppositeend o fth'e' casing'lllfr'orn the bearing 5" a-se'cond bearing "HI for the'shaft' H"? isprovided; While the particular construction 'of thebearing and itscompanion parts which form" the seal for the casing ID are the subjectmatter" of Patent No. 2,254,862 issued September 2, 1941-,: thestructu're'wi'll,jbespecitically described hereinf toestablish'i'ts'actionf andcooperation the general combination is the'comnresser.

a The" bearing ro lsa tight fitting bearing a d 1 since the mach-indie:this typei the shaft fre quently getsslig'htly outof alignment duevarious causes such? as] whip theshaf t when rotating athigh 'speeds',means 'are provided to n b e a i iiuesiso as torO- videan"effective"seal for theshaft opening in th casing. '1' The bearing is'cohrie'cted to thepas I 1 mg m by a flexible disc"II. "'1hisf-disc made1 of strong, flexible metal sothat twninex d ring;

:shaft to preservegthe seal jan'd-to; prevent V exce'ss'f wear onthebearing. Thes haft opening .51 opens intoa chamber 1.2, into which theinner end of the bearing Ill also extends, while'theoiiterf of "thebearing" extends into'a'chamber 1 3 The teha'mber "is subjectedto'a'pres'sure'of apprexi? mat'ely atmosphere; that i'sj'a' pressureslightly above' orbelow atmosphere, namely the suction pressure'ofthevapor atthe'inlct of the impeller: 39; while 'the chamber13"is'subjectedto atmo ofthe bearing 10' intermediate its enqs rem ,th"jfl oil-inlet line 14 through a suitablefconnection15; f The inlet line14 receives oil fronr t he o'utletiendf J of the oil cooler 60'.'Theoil'passesiongitudiiially"e I fm i t e bearing i (bl t d r io s; rof t. passing into the 'chamber '12 from which it drains,

through" suitabledrain outlets 1T; "ai'i Ri e con f nections :18 to=a'"collecti'on "che'n'nberjl9; Fr'o m'fQ thatchan'iber'lil theoil'returns'to thejres'e ryoir 5152 through the pipe'system" 80. The oilwhichg' g flo'ws outwardly through' thej bearingfint o th e chamber-'l3"passes through suitable drain open-.4" ingjs 8| into the collectionchamber '82", from which it-passe's through the collection piping sysl-The interior of the oil chamber 52 is under th"\ ,2 'same pressure asthe shaft 'open 1' ng 5 0, 'v'i'z .,"the. "v pressure of the vapor atthe'initial'inletjto the compressor. By having'it under such relativelylow pressure refrigerant which is carried thereto by the oil and isconsequentlydeliveredto the" chamber at a pressure in excess of the"pressure therein-isreleas'edi h,

A bushing is positioned betweenthe charn-', Q

bBT 1.2 and the impeller" 39 ,"s imilar in its con; 1"

struction to the bushing 66, having a, plurality of annular grooves 84spaced longitudinally along its bore, and is provided with an oncollection chamber at from which oil drains through a suit 'a51e--arem 6into the chamber 12 The b g .1

83' forms agd'amtd -hinder leakage of oiljinto the suction oftheimpeller 39. c E- e construction of, the bearing n'andthes lubricationof the: bearing in the menheeflebove described will effectively seal theopening 5| from both leakage of vapor out of the casing and leakage ofair into the casing, during the operation of the compressor. But whenthe compressor is shut down the delivery of lubricating oil to thehearing will be stopped and consequently it is necessary to providemeans to prevent either internal leakage of air or external leakage ofvapor out of the casing through the opening 5| at such times. 7

The structure provided for this purpose in cludes a packing collar 90,which is of any suitable type of soft, resilient material notsusceptible to objectionable corrosion or deterioration under action ofthe refrigerant vapor compressed. There are many substances of whichthis collar may be constructed, such as Neoprene and the like. This softresilient packing collar 90 snugly fits about the shaft II and its in--ner side near its periphery contacts an annular of the compressor thetension of the spring 98 is overcome by the pressure of oil from thelubricating system of the compressor, which is delivered to the interiorof the bellows 91 through the connection 99, thus expanding the bellowsand forcing the piston 96 outwardly, which moves the sleeve 93outwardly, relieving the soft, resilient packing collar 90 of pressurefrom the sleeve 93. When'the compressor is stopped and consequently thepressure of oil in the bellows 91 is relieved, the spring 98 will movethe piston 96 inwardly and through the medium of the lever 94 force thesleeve 93 inwardly against the collar 90, tightly squeezing the collaragainstthe shaft to form a tight seal about the shaft. For the purposeof insuring the movement of the packing collar 90 into a pressurerelieved position during the operation of the compressor, a follower I0!is mounted about the shaft II and engages the inner side of the collar90 inwardly of the shoulder 9|. A spring I02 engages the follower I01for urging it outwardly thus moving the collar 90 out of tight sealingengagement with the shaft when the collar is relieved of pressure of thesleeve 93.

A dish-shaped slinger I03 is mounted on the shaft H for rotationtherewith,between the collar 90 and the bearing 10, and in the chamber13. This dish-shaped slinger I03 is provided for throwing oil away fromthe shaft li so as to preventoil from leaking along the shaft to thecollar 90. v

It will be understood that the invention is not to be limited to thespecific construction or arrangement of parts shown, but that they maybe widely modified within the invention defined by the claims.

What is claimed is:

1. In a multi-stage centrifugal machine for compressing gas or vapor, acasing, three stage impellers in said casing, the first and second stageimpellers arranged in'a set with their discharge sides facing thedischarge side of the third stage impeller and having combined dischargepressures approximately equal to the discharge pressure of the thirdstage.

compressing gas or vapor, a casing, three stage impellers in saidcasing, the first and second stage impellers arranged in a set withtheir discharge sides facing the discharge side of the third stageimpeller and having combined discharge pressures slightly greater thanthe discharge pressure of the third stage impeller to substantiallybalance end thrust by leaving a small unbalance of end thrust to avoidreversal of thrust during operation.

3. In a multi-stage centrifugal machine for compressing gas or-vapor, acasing, three stage impellers in said casing, the first and second stageimpellers arranged in a set with their discharge s ides facing thedischarge side of the third stage impeller and having combined dischargepressures approximately equal to the discharge pressure of the thirdstage, said first stage impeller having a twin volute casing with thetwothroat sections thereof disposed approximately apart, the second andthird stage impellers each having a single volute casing, said single,volute casings being angularly disposed with their throat sectionsarranged relative to each other so that the side thrusts of one voluteare counterbalanced by the side thrusts of the other volute.

4. In a multi-stage centrifugal machine for compressing gas or vapor, acasing, three stage impellers in said casing,the first and second stageimpellers arranged in a set with their discharge sides facing thedischarge side of the third stage impeller and having combined dischargepressures approximately equal to the discharge pressure of the thirdstage, said first stage impeller having a twin volute'casing with thetwo throat sections thereof disposed approximately 180 apart, the secondand third stage impellers each having a single volute casing, saidsingle volute casings being angularly disposed with their throatsections arranged relative to each other so that the side thrusts of onevolute are counterbalanced by the side thrusts of the other .volute,said second andthird stage impellers being disposed back-to-back and inclose relation to each other whereby the side thrusts of the two volutesare approximately in the same plane.

5. In a multi-stage centrifugal machine for compressing gas or vaporwherein the pressure of material compressed increases in geometricproes's fln m stage'to stage with the absolute proximately equalize theend thrust of the impellers.

6. In a multi-stage centrifugal machine for compressing gas or vaporwherein the pressure of material compressed increases in geometricprogression from stage to stage with the absolute discharge pressure ofeach stage bearing a substantially constant ratio to its inlet pressure,a casing, a plurality of impellers of substantially equal diameter insaid casing, said impellers arranged in sets of unequal numbers ofimpellers with the impellers in each set constituting successive stagesof compression and with the impellersin one set disposed in back to backrelation with the impellers of the other set and with the total absolutedischarge pressure of one set being slightly greater than the totalabsolute discharge pressure of the other set to substantially balanceend thrust but leaving a small unbalance of end thrust to avoid reversalof thrust during operation.

'7. In a muiti-stage centrifugal machine for compressing gas or vapor, acasing, three stage impellers in said casing, the first and second stageimpellers arranged in a set with their discharge sides facing thedischarge side of the third stage impeller and having combined dischargepressure approximately equal to the discharge pressure of the thirdstage, the discharge stage and oneother of the stages of the compressorbeing provided with single discharge volutes arranged relative to eachother to balance .side thrusts oi the said stages, the remaining stage01' said compressor being provided with a twin discharge volute with thetwo throat sections thereof disposed relative to each other to balancethe 7 side thrust of said stage of the compressor.

8. In a multi-stage centrifugal machine for compressing gas or vaporwherein the pressure of fluid compressed increases in geometricprogression from stage to stage with the absolute discharge pressure ofeach stage bearing a substantially constant ratio to its inletpressure,acasing, a plurality of stage impellers in said casing, saidimpellers having progressively decreased volumetric capacity from theinlet stage to the final discharge stage. said impellers arranged insets of unequal numbers of impellers with the impellers in each setconstituting successive stages of compression, the impellers of one set.having combined discharge pressures approximately equal to the combineddischarge pressures oi. the other set and arranged to substantiallybalance end thrust during operation 01' the compressor.

9. In a multi-stage centrifugal machine for compressing gas or vaporwherein the pressure of fluid compressed increases ingeometricprogression from stage to stage with the absolute discharge pressure ofeach stage bearing a substantially constant ratio to its inlet pressure,.a casing, a plurality 'of stage impellers in said casing, saidimpellers having progressively decreased volumetric capacity fromtheinlet stage to the final discharge stage, said impellers arranged insets of unequal numbersot impellers with the impellers in each setconstituting successive stages of compression, the impellers of one sethaving combined discharge pressures approximately equal to the combineddischarge pressures ofthe other set and arranged to substantiallybalance end thrust during operation of the compressor. one of saidstages of the larger volumetric capacity having a twin discharge volute,and the remaining stages being provided with single discharge voiutesarranged relative to each other to balance side thrusts of the stages. I

RALPH M. WATSON. I

